Ink ribbon cassette

Abstract: One of a ribbon feed roller (32) and a pressure roller (34) for making an endless ink ribbon (30) run is displaceable relative to the other roller thereof for facilitation of replacement of the ink ribbon (30), and can be locked at a withdrawn position thereof. In a state where one roller is locked at the withdrawn position, mounting of the ink ribbon cassette on a printer is obstructed. Also, a running direction and an orientation of the endless ink ribbon (30) are defined so that damage to the bonded portion of the endless ink ribbon (30) is delayed as much as possible.

Description: The present invention relates to an ink ribbon cassette for an impact printer such as a serial wire-dot printer. In recent years, in contrast to the fact that more compact ink ribbon cassettes are required because impact printers are becoming more compact, there is a demand for the service life of the ink ribbon to be prolonged. To respond to this requirement, the ink ribbon cassette disclosed in Japanese Unexamined Utility Model Publication No. 62-128850 and in Japanese Unexamined Utility Model Publication No. 63-51756 uses an endless ink ribbon. In this type of ink ribbon cassette, there is an ink ribbon storage unit, which stores the ink ribbon in a zigzag manner, and an ink ribbon passage which extends from a first side towards a second side of the ink ribbon storage unit. Where the ink ribbon is made to run from the first side of the ink ribbon storage unit through the ink ribbon passage to the second side thereof, a ribbon feed roller is provided on the second side of the ink ribbon storage unit. A pressure roller is elastically pressed against the ribbon feed roller. The ribbon feed roller is arranged in such a manner that the ink ribbon is wound therearound over substantially a half circumference thereof, with the pressure roller being elastically pressed against the ink ribbon. When this ink ribbon cassette is mounted on the carriage of a printer, a drive shaft projecting from the carriage is received, and engages, in a hole in the ribbon feed roller. During printing, the ribbon feed roller is driven to rotate in a predetermined direction by the drive shaft, whereby the ink ribbon is drawn from one side of the ink ribbon storage unit through the ink ribbon passage to the other side of the ink ribbon storage unit where it is stored. With this arrangement, the ink ribbon can be used over a long period of time until it reaches the end of its service life, i.e. when it physically breaks. Moreover, to save natural resources, it is also general practice to make it possible to replace the ink ribbon in the ink ribbon cassette. In this case, the ink ribbon cassette per se can be used semi-permanently. An ink ribbon cassette with a replaceable ink ribbon is constituted so that, when the ink ribbon is to be replaced, the pressure roller is locked in a withdrawn position at a distance from the ribbon feed roller. This enables the replacement of the ink ribbon to be easily carried out by the user. However, after replacing the ink ribbon, the user is liable to make a mistake by mounting the ink ribbon cassette on the printer while the pressure roller is locked in the withdrawn position. As a result, the ink ribbon cannot run through the ink ribbon passage and therefore the printing impact is concentrated only on a specific portion of the ink ribbon. Even if the user becomes aware of this mistake and makes adjustments to allow the ink ribbon to run, the portion on which the impact is concentrated is weaker than the rest of the ribbon and thus the service life of the ink ribbon is shortened. On the other hand, an endless ink ribbon is formed by bonding the two ends of a long length of an ink ribbon by ultrasonic bonding. When this bonded portion is subjected to printing impact, the bonded portion is liable to be damaged earlier than the other portions. This tendency is more conspicuous as the printing speed increases. Accordingly, to respond to the demand for high speed printing in recent years, it has been demanded that the damage to such a bonded portion is reduced as much as possible. Accordingly, an object of the present invention is to provide an ink ribbon cassette which uses an endless ink ribbon and is arranged such that it cannot be mounted on a printer in such a state that the endless ink ribbon cannot be moved after the ink ribbon has been replaced. According to the present invention, there is provided an ink ribbon cassette, comprising: ink ribbon storage means for storing an endless ink ribbon; ink ribbon passage means extending from a first side of the ink ribbon storage means to a second side thereof; a ribbon feed roller and a pressure roller provided at the second side of the ink ribbon storage means for making an ink ribbon run from the first side of the ink ribbon storage means to the second side thereof through the ink ribbon passage means, one of the ribbon feed roller and the pressure roller being displaceable between a pressing position in which said one roller is elastically pressed against the other roller and a withdrawn position in which said one roller is retracted from the pressing position; and locking means for releasably locking said one roller in the withdrawn position, characterised in that the roller which is displaceable is a drive roller and the other roller is a driven roller. In the ink ribbon cassette of the invention, the roller which is displaceable is the drive roller and the other roller is the driven roller. Preferably, the drive roller includes a shaft element which has an engagement hole formed therein for receiving the drive shaft of a printer, the arrangement being such that, if the ink ribbon cassette is mounted on the printer while the drive roller is in the withdrawn position, the drive shaft cannot be received in the engagement hole. The displaceable roller may be rotatably supported by a movable support member. In this case, the movable support member is provided with at least one plate spring element having a claw element, the claw element engaging with a hole formed in the side wall of the ink ribbon storage means when the displaceable roller is in the withdrawn position to lock the displaceable roller in the withdrawn position. The plate spring element may have an extension portion which projects out of the side wall of the ink ribbon storage means when the claw element is engaged with the hole and interferes with a structure of the printer if the ink ribbon cassette is mounted on the printer. The ink ribbon cassette of the invention may be provided in combination with an endless ink ribbon which is formed by superimposing and ultrasonically bonding end portions of a long length of an ink ribbon made of a fabric of a synthetic resin fibre such that one side part of the bonded portion of the endless ink ribbon is molten and resinified as a solid part, and the other side part thereof is brought to a semi-molten state as a semi-solid part, the running direction and the orientation of the endless ink ribbon being defined so as to avoid a passing mode where a printing head of the printer passes the resinified solid part of the bonded portion in a non-opposed direction when the ink ribbon cassette is mounted on a printer. For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:- Figure 1 is a partially cutaway plan view of an ink ribbon cassette according to the present invention, showing the pressure roller locked in a withdrawn position; Figure 2 is a bottom view of the ink ribbon cassette of Fig. 1; Figure 3 is a rear view of the ink ribbon cassette of Fig. 1; Figure 4 is a front view of the ink ribbon cassette of Fig. 1; Figure 5 is a partially enlarged cross-sectional view taken along the line V-V in Fig. 3; Figure 6 is a plan view similar to Fig. 1, but showing the pressure roller in the pressing position with respect to the ribbon feed roller; Figure 7 is a bottom view of the ink ribbon cassette of Fig. 6; Figure 8 is a plan view of a modified embodiment of the ribbon feed roller and the pressure roller provided inside the ink ribbon cassette of Fig. 1; Figure 9 is a right side view of the modified embodiment of Fig. 8; Figure 10 is a plan view of another modified embodiment of the ribbon feed roller and the pressure roller provided inside the ink ribbon cassette of Fig. 1; Figure 11 is a plan view similar to Fig. 10, but showing the pressure roller locked in the withdrawn position thereof; Figure 12 is a partial plan view of another embodiment of the ribbon feed roller and the pressure roller of the ink ribbon cassette according to the present invention; Figure 13 is a schematic view of an ultrasonic bonding procedure in which an endless ink ribbon is formed from a long strip of an ink ribbon; Figure 14 is a side view of the bonded portion of the endless ink ribbon; Figure 15A is a plan view showing one side part of the bonded portion of the endless ink ribbon; Figure 15B is a plan view showing the other side part of the bonded portion of the endless ink ribbon; Figure 16A is a partial perspective view of the side part shown in Fig 15A; Figure 16B is a partial perspective view of the side part shown in Fig 15B; Figure 17 is a schematic view of the relative relationship between the running direction of the ink ribbon and the direction of movement of the printing head; Figure 18A is a plan view and a side view of the bonded portion of an endless ink ribbon for explaining the passing mode of a printing head of a wire-dot printer with respect to the bonded portion; Figure 18B is a plan view and a side view of the bonded portion of an endless ink ribbon for explaining another passing mode of the printing head with respect to the bonded portion; Figure 18C is a plan view and a side view of the bonded portion of the endless ink ribbon for explaining a further passing mode of the printing head with respect to the bonded portion; and Figure 18D is a plan view and a side view of the bonded portion of the endless ink ribbon for explaining a still further passing mode of the printing head with respect to the bonded portion. Referring to Figs. 1 to 7, a preferred embodiment of the ink ribbon cassette according to the present invention is shown. This ink ribbon cassette is provided with a casing 10 and a cover 12, which are formed of a suitable synthetic resin material, such as an ABS resin. The upper side of the casing 10 is open, and the cover 12 is detachably attached to the casing 10 so as to cover the open upper side thereof. As is apparent from Fig. 1 and Fig. 2, the casing 10 includes a rectangular part 10a, a first arm 10b projecting from a first side of the rectangular part 10a, and a second arm 10c projecting in the same direction from a second side of the rectangular part 10b. The cover 12 is constituted to be substantially the same shape as the shape of the casing 10. Thus, the cover 12 includes a rectangular part 12a, and first and second arms 12b and 12c projecting from the corresponding sides of the rectangular part 12a. As best illustrated in Fig. 3, for detachably attaching the cover 12 to the casing 10, three projections 14 are integrally formed along the top edge of the rear wall of the rectangular part 10a of the casing 10, while three tongue pieces 16 integrally project from the rear edge of the rectangular part 12a of the cover 12 along the rear wall of the rectangular part 10a of the casing 10. Each projection 14 fits into a slot hole formed in the corresponding tongue piece 16. Also, as shown in Fig. 1, a projection 18 is formed integrally on the front wall of the rectangular part 10a of the casing 10 along the top edge thereof, while a tongue piece 20 integrally projects from the front edge of the rectangular part 12a of the cover 12. The projection 18 fits into slot holes formed in the tongue piece 20. Further, as shown in Fig. 1 and Fig. 4 projections 22b and 22c are formed from the outside wall on the front side of the first and second arms 10b and 10c of the casing 10, respectively, while tongue pieces 24b and 24c integrally project from the front edges of the first and second arms 12b and 12c of the cover 12, respectively. The projections 22b and 22c fit into slot holes formed in the tongue pieces 24b and 24c. As is apparent from Fig. 4, a pair of slits is formed in each of the outside walls on the front side of the first and second arms 10b and 10c of the casing 10 so as to form plate spring elements 26b and 26c. Top edges of the respective plate spring elements 26b and 26c form the projections 22b and 22c. The attachment and detachment of the cover 12 with respect to the casing 10 can be relatively easily carried out by elastic deformation of plate spring elements 26b and 26c. As can be seen from Fig. 1 and Fig. 2, the rectangular part 10a of the casing 10 is provided with a pair of plate spring members 28 which integrally project from the rear ends of the two side walls thereof and extend substantially parallel to the two end walls of the rectangular part 10a. An end shaft 28a is formed on the outside of the end of each plate spring member 28. In the present embodiment, the ink ribbon cassette is mounted on the carriage of a serial wire-dot printer (not shown). At the time of mounting, the end shafts 28a of the plate spring members 28 are attached to the positioning hole provided in the carriage of the printer. Note that, when the ink ribbon cassette is mounted on the carriage, the wire-dot printing head is located in a space defined by the first and second arms 10b and 10c of the casing 10. As shown in Fig. 1, an endless ink ribbon 30 is accommodated in the casing 10. The rectangular part 10a of the casing 10 acts as an ink ribbon storage unit for storing the endless ink ribbon 30 in a zigzag manner, and the first and second arms 10b and 10c of the casing 10 form an ink ribbon passage. The ink ribbon is exposed in the space between the ends of the first and second arms 10b and 10c. The ink ribbon is made to run across the printing surface of the wire-dot printing head at that exposed portion. In the present embodiment, the endless ink ribbon 30 is formed by bonding together the two ends of a long length of an ink ribbon by ultrasonic bonding. One of the two ends of the ink ribbon is twisted exactly one half turn with respect to the other, and thus the endless ink ribbon 30 forms a so-called Möbius strip. Accordingly, a twist 30a is produced in the endless ink ribbon 30. The twist is accommodated and restrained inside the first arm 10b of the casing 10, as shown in Fig. 1. By forming the endless ink ribbon 30 as a Möbius strip, the printing impact on the endless ink ribbon 30 is dispersed in the width direction thereof, and thus the service life of the endless ink ribbon 30 can be prolonged. As shown in Fig. 1, on one side of the rectangular part 10a of the casing 10, that is near the second arm side 10c, a ribbon feed roller 32 and a pressure roller 34 are provided adjacent each other. As best shown in Fig. 5, the ribbon feed roller 32 is constituted by a shaft element 32a rotatably supported with respect to the bottom portion of the casing 10, a pair of rubber roller elements 32b fixed on the shaft element 32a, and a gear element 32c formed integrally with the shaft element 32a. The top end of the shaft element 32a projects to the outside through an opening formed in the cover 12, as shown in Fig. 5 and Fig. 6, and a knurl 32d is formed on that projecting part. The bottom end 32e of the shaft element 32a is rotatably attached to a hole formed in the bottom portion of the casing 10, as shown in Fig. 2, Fig. 5 and Fig. 7. The pressure roller 34 is constituted by a shaft element 34a rotatably supported by a movable frame assembly 36, a pair of rubber roller elements 34b fixed on the shaft element 34a, and a gear element 34c formed integrally with the shaft element 34a. An upward projection 36a and a downward projection 36b project integrally from the movable frame assembly 36. The upward projection 36a is slidably accommodated in an elongate hole 37a formed in the cover 12 (see Fig. 5 and Fig. 6) and the downward projection 36b is slidably accommodated in an elongate hole 37b formed in the bottom portion of the casing 10 (see Fig. 2, Fig. 6, and Fig. 7). Accordingly, the pressure roller 34 is slidable in a forward and backward direction with respect to the ribbon feed roller 32. As shown in Fig. 5, a compression coil spring 38 is provided between the rear side wall of the rectangular part 10a of the casing 10 and the movable frame assembly 36. The coil spring 38 functions to press the pressure roller 34 elastically against the ribbon feed roller 32 (see Fig. 5, Fig. 6, and Fig. 7), whereby both of the pairs of rubber rollers 32b and 34b are frictionally engaged with each other and the two gear elements 32c and 34c are engaged with each other. As shown in Fig. 2 and Fig. 7, the bottom end of the shaft element 34a of the pressure roller 34 is exposed through an opening 39 formed in the bottom portion of the casing 10, and has an engagement hole 34d for non-rotatably receiving a drive shaft 40 (Figs. 2 and 5) provided in the carriage of the printer. In short, the rotational drive force of the drive shaft 40 is transmitted to the ribbon feed roller 32 via the engagement of the gear elements 32c and 34c. As is apparent from Fig. 2 and Fig. 7, the elongate hole 37b accommodating the downward projection 36b of the movable frame assembly 36 continuously extends to the opening 39 through which the bottom end of the shaft element 34a of the pressure roller 34 is exposed to the outside. When the drive shaft 40 is driven in the direction indicated by the arrow shown in Fig. 5, the ribbon feed roller 32 and the pressure roller 34 are rotated and pull the ink ribbon from the second arm part 10c of the casing 10 to the rectangular part 10c thereof, that is, the ink ribbon storage unit 10a. As is apparent from Fig. 1, the ink ribbon feed roller 32 is arranged in such a manner that the ink ribbon 30 is wound around the ribbon feed roller 32 over substantially half the circumference thereof, whereby the ink ribbon 30 can run without slipping with respect to the ribbon feed roller 32. To eliminate entanglement of the ink ribbon 30 around the ribbon feed roller 32 during rotation thereof, a separator 42 is interposed between the rubber rollers 32b of the ribbon feed roller 32, as shown in Fig. 5. The separator 42 is appropriately supported within the casing 10. A chamber filled with a felt material 44 is provided in a part inside the second arm 10c of the casing 10. The felt material 44 is impregnated with ink and has a felt core material 44a provided therein which projects from the above-mentioned chamber and into contact with one of the pair of rubber rollers 32b of the ribbon feed roller 32. The ink impregnated in the felt material 44 is supplied through the felt core material 44a to the rubber roller 32b by capillary action and is absorbed by the ink ribbon 30. In short, the felt material 44 acts as an ink supply source. When the service life of the ink ribbon 30 reaches its end, that is, when the ink ribbon 30 is damaged to such an extent that it cannot perform proper printing, the ink ribbon 30 must be replaced by a new one. The movable frame assembly 36 supporting the pressure roller 34 is moved backwards so as to move away from the ribbon feed roller 32 against the spring force of the compression coil spring 38. Such a movement of the movable frame assembly 36 is carried out by nipping the upward projection 36a and the downward projection 36b thereof between, for example, a thumb and a forefinger and pulling the same backward. When the movable frame assembly 36 is retracted to the predetermined position relative to the ribbon feed roller 32, the movable frame assembly 36 is locked at that retracted position. In particular, each of a pair of plate spring elements 36c projects integrally from the two sides of the movable frame assembly 36, with a claw element 36d being formed at a free end of each plate spring element 36c. When the movable frame assembly 36 is retracted, the claw elements 36d of the plate spring elements 36c pass through slot holes formed in the rear side wall of the rectangular part 10a of the casing 10. Each claw element 36d becomes engaged with the corresponding slot hole thereof, whereby the pressure roller 34 is locked in the withdrawn position, as shown in Fig. 1 and Fig. 2. When the cover 12 is removed from the casing 10 in this state, there is a predetermined clearance between the ribbon feed roller 32 and the pressure roller 34 (see Fig. 1), whereby the replacement of the ink ribbon 30 can be smoothly and easily carried out. After the replacement of the ink ribbon has been completed, the cover 12 is reattached to the casing 10 and the pressure roller 34 is returned from the withdrawn position to the pressing position. This is carried out by pushing the claw elements 36d of the plate spring elements 36c together, for example, by pressing with the thumb and forefinger. When pushed together, the respective claw elements 36d are released from engagement with their corresponding slot holes and, as a result, the movable frame assembly 36 is restored to the pressing position with respect to the ribbon feed roller 32 by the compression coil spring 38. Thereafter, the ink ribbon cassette is mounted on the carriage of the printer with the drive shaft 40 on the carriage being received in the engagement hole 34d of the shaft element 34a of the pressure roller 34, as shown in Fig. 5. The user is prevented from mounting the ink ribbon cassette on the carriage of the printer when the pressure roller 34 is locked in the withdrawn position. This is because, when the pressure roller 34 is in the withdrawn position, the engagement hole 34d formed in the bottom end of the shaft element 34a is not in alignment with the drive shaft 40, as is apparent from the comparison of Fig. 2 with Fig. 7. As shown in Fig. 5, the engagement hole 34d of the shaft element 34a is allowed to receive the drive shaft 40 only when the pressure roller 34 is in the pressing position with respect to the ribbon feed roller 32, whereby mounting of the ink ribbon cassette on the carriage of the printer becomes possible. Thus, according to the present invention, the ink ribbon cannot be in a non-running state after the ink ribbon cassette is mounted on the printer, and therefore the printing impact will not be applied to only one specific portion of the ink ribbon, as in the conventional cassette. Referring to Fig. 8 and Fig. 9 where like reference numerals indicate like parts, a modified embodiment of the ribbon feed roller 32 and the pressure roller 34a is shown. In this modified embodiment, rubber roller elements 34b of the pressure roller 34 are frictionally engaged with rubber roller elements 32b of the ribbon feed roller 32, and the rotational drive force of the drive shaft 40 is transmitted to the ribbon feed roller 32 by the friction force between them. Referring to Fig. 10 and Fig. 11, a modified embodiment of the movable frame assembly 36 is shown. In this modified embodiment, an extension portion 36e is added to the free end of the pair of plate spring elements 36c projecting from the movable frame assembly 36. The extension portion 36e interferes with the structure 46 of the carriage when an attempt is made to mount the ink ribbon cassette on the carriage of the printer when the pressure roller 34 is locked in the withdrawn position, thereby obstructing the mounting of the ink ribbon cassette on the carriage. This modified embodiment is advantageous particularly where the ribbon feed roller 32 is a drive roller, i.e., where the ribbon feed roller 32 has an engagement hole for receiving the drive shaft on the carriage of the printer (see below). Referring to Fig. 12, another embodiment according to the present invention is shown. In this embodiment, the ribbon feed roller 32 is rotatably supported by a movable bracket 48, and the pressure roller 34 is rotatably supported in a position fixed relative to the casing 10. The movable bracket 48 can pivot freely around a pivot 50 and, in addition, is elastically biased against the pressure roller 34 by a compression coil spring 38. A plate spring element 48a integrally extends from the movable bracket 48, and projects through a hole formed in the front wall of the rectangular part 10a of the casing 10. A claw element 48b is formed on the plate spring element 48. When the movable bracket 48 is pivoted in the clockwise direction in Fig. 12, the claw element 48b engages with the above-mentioned hole and causes the ribbon feed roller 32 to lock in a withdrawn position away from the pressure roller 34. The bottom end of the shaft element of the ribbon feed roller 32, which has a bore for receiving the drive shaft of a printer, is exposed from the bottom portion of the casing 10. Accordingly, when the ribbon feed roller 32 is locked in the withdrawn position, the ink ribbon cassette cannot be mounted on the carriage of a printer. The present embodiment has been described with reference to an ink ribbon cassette which is mounted on the carriage of the printer. It goes without saying that the present invention can also be applied to a so-called installed type ink ribbon cassette which is mounted on the printer per se. Referring now to Fig. 13, an endless ink ribbon formed by ultrasonically bonding the two end portions 52 and 54 of a long length of ink ribbon is illustrated. In this drawing, reference numeral 56 indicates an ultrasonic oscillation horn, and reference numeral 58 indicates a bonding stand. The ink ribbon per se is formed by a fabric made of a nylon fibre. After the two end portions 52 and 54 of the ink ribbon are superimposed on each other and ultrasonically bonded, the excess ribbon on the two sides of the bonded portion is cut and removed. Figure 14 schematically illustrates such a bonded portion of the endless ink ribbon after the excess ribbon has been removed therefrom. In Fig. 14, one part of the bonded portion, indicated by reference numeral 52' and shown as a black solid area, is the side to which the ultrasonic bonding oscillation horn 56 was applied, and is completely molten and formed into a resin. On the other hand, the other part of the bonded portion, indicated by reference numeral 54' and shown as a hatched area, is the side to which the bonding stand 58 was applied, and was brought into a semi-molten state in which the texture thereof remains. The respective parts 52' and 54' of the bonded portion will be referred to hereinafter as the solid part and the semi-solid part. As shown in Fig. 15A and 15B, the bonded portion (52', 54') is inclined with respect to the longitudinal direction of the ink ribbon. The outer appearance of the bonded portion (52', 54') is shown in Fig. 16A and Fig. 16B. It is well known that ultrasonic energy is moderated by interposing paper, a film, or the like on and below the superimposed end portions of the ink ribbon when ultrasonic bonding is carried out. However, even in this case, the bonded portion still has the characteristics described above. In Fig. 17, numeral 60 indicates the platen of a printer, P indicates a sheet of paper, arrow W indicates the running direction of the ink ribbon, and numeral 62 indicates the printing head of a serial wire-dot printer. The printing head 62 will perform the printing operation in both a CR and SP direction. On the other hand, the printing head 62 can pass over the bonded portion (52', 54') of the ink ribbon in one of two possible modes with respect to each part 52', 54' of the bonded portion, depending on the running direction of the ink ribbon and the orientation thereof. In particular, regarding the solid part 52', there are two passing modes: one where the wires 64 of the printing head 62 face the end face of the solid part 52' and then pass over the solid part 52', as shown in Fig. 18A; and the other where the wires 64 of the printing head 62 pass over the bonded portion from the side opposite to the end face of the solid part 52', as shown in Fig. 18B. Similarly, regarding the semi-solid part 54', there are two passing modes: one where the wires 64 of the printing head 62 face the end face of the semi-solid part 54' and then pass thereover, as shown in Fig. 18C; and the other where the wires 64 of the printing head 62 pass over from the side opposite the end face of the bonded portion 54', as shown in Fig. 18D. For convenience of explanation, the following is assumed: for the passing modes shown in Fig. 18A and 18C, it is defined that the printing head 62 passes in the opposed direction with respect to the bonded portion, and for the passing modes shown in Fig. 18B and 18D, it is defined that the printing head 62 passes in the non-opposed direction with respect to the bonded portion. A damage test was carried out for each of the four passing modes mentioned above, and an evaluation was carried out for the degree of damage. The results are in the following table: Number of printed letters (Unite: 10,000) Passing mode bonded portion Fig. 18A Fig. 18B Fig. 18C Fig. 18D 500 o ○ o ○ o ○ o ○ 600 o ○ ○ o ○ ○ 700 o ○ ○ o ○ ○ 800 o ○ ○ o ○ ○ 900 o ○ ○ o ○ ○ 1000 o ○ X o ○ ○ 1100 o ○ X o ○ ○ 1200 o ○ X o ○ ○ 1300 o ○ X ○ ○ 1400 o ○ X ○ ○ 1500 o ○ X ○ ○ 1600 o ○ X ○ ▴ 1700 o ○ X ○ ▴ 1800 ○ X ○ X 1900 ○ X ○ X 2000 ○ X ○ X Symbol "o ○" indicates "no problem"; symbol "○" indicates a state where the ink ribbon fabric becomes thinner in a narrow region adjoining the bonded portion thereof; symbol "▴" indicates a state where the ink ribbon fabric becomes thinner in a relatively wide region adjoining the bonded portion thereof; and symbol "X" indicates a state where holes of 0.2 mm or less are generated in a region adjoining the bonded portion of the ink ribbon. Where the evaluation is "▴" or "X", the ink ribbon is not durable in use and must be replaced by a new ink ribbon. It can be seen from the above results that the passing mode shown in Fig. 18B must be avoided. In the case of the passing mode of Fig. 18B, the wires of the printing head intensively pull and strike the root of the resinified bonded portion. Therefore the boundary between the resinified portion and the fabric portion is likely to be broken. The endless ink ribbon is generally formed into a so-called Möbius strip so as to prolong the service life by making the used position thereof uniform: both strip zones of the ink ribbon divided by a longitudinal neutral line thereof are used as the printing zone. In this case, one of two combinations of the four passing modes as shown in Fig. 18A through Fig. 18D occurs. These combinations are either where the passing modes of Fig. 18A and Fig. 18D alternately appear or where the passing modes of Fig. 18B and Fig. 18C alternately appear. Of course, to prolong the service life of the ink ribbon, the combination of passing modes of Fig. 18A and Fig. 18D must be selected. Where the endless ink ribbon is formed as a simple ring, the passing mode of Fig. 18B should be avoided and the passing mode should be selected from the modes shown in Fig. 18A, Fig. 18C, or Fig. 18D. As is apparent from the above disclosure, according to the present invention, the ink ribbon cassette is reliably obstructed from being mounted on the carriage of the printer while the endless ink ribbon is in a non-running state, and therefore a situation where only a specific position of the ink ribbon is subjected to the printing impact can be avoided. Also, according to one embodiment of the present invention, the running direction and orientation of the ink ribbon are defined in accordance with the characteristic of the bonded portion of the endless ink ribbon. In this way, it is possible to delay the damage to the ink ribbon at the bonded portion thereof as much as possible. In short, according to the present invention, it becomes possible to prolong the service life of the endless ink ribbon to the maximum level.

Claims: An ink ribbon cassette, comprising: ink ribbon storage means (10a) for storing an endless ink ribbon (30); ink ribbon passage means (10b, 10c) extending from a first side of the ink ribbon storage means (10a) to a second side thereof; a ribbon feed roller (32) and a pressure roller (34) provided at the second side of the ink ribbon storage means (10a) for making an ink ribbon (30) run from the first side of the ink ribbon storage means (10a) to the second side thereof through the ink ribbon passage means (10b, 10c), one of the ribbon feed roller (32) and the pressure roller (34) being displaceable between a pressing position in which said one roller is elastically pressed against the other roller and a withdrawn position in which said one roller is retracted from the pressing position; and locking means for releasably locking said one roller in the withdrawn position, characterised in that the roller which is displaceable is a drive roller and the other roller is a driven roller. An ink ribbon cassette as claimed in claim 1, wherein, in the pressing position, the drive roller is frictionally engaged with the driven roller so as to transmit the rotational drive force of the drive roller to the driven roller. An ink ribbon cassette as claimed in claim l or claim 2, wherein the drive roller and the driven roller are each provided with gear elements which engage when the drive roller is in the pressing position and transmit the rotational drive force of the drive roller to the driven roller. An ink ribbon cassette as claimed in claim 1, 2 or 3, wherein the drive roller is rotatably supported by a movable support member (36; 48) which is provided with at least one plate spring element (36c; 48a) having a claw element (36d, 48b), the claw element (36d, 48b) engaging a hole formed in a side wall of the ink ribbon storage means (10c) when the drive roller is in the withdrawn position to lock the drive roller in the withdrawn position. An ink ribbon cassette as claimed in claim 4, wherein the or each plate spring element (36c) has an extension portion (36e) which projects out of the side wall of the ink ribbon storage means (10a) when the claw element (36d) is engaged with the hole and interferes with a structure of a printer if the ink ribbon cassette is mounted on the printer. An ink ribbon cassette as claimed in claim 3, 4 or 5, wherein the ribbon feed roller (32) is the driven roller, and the pressure roller (34) is the displaceable drive roller rotatably supported by the movable support member (36). An ink ribbon cassette as claimed in any preceding claim, wherein the drive roller includes a shaft element (34a) which has an engagement hole (34d) formed therein for receiving the drive shaft (40) of a printer, the arrangement being such that, if the ink ribbon cassette is mounted on the printer while the drive roller is in the withdrawn position, the drive shaft (40) cannot be received in the engagement hole (34d). An ink ribbon cassette as claimed in any preceding claim, wherein the ribbon feed roller (32) and the pressure roller (34) each comprise a cylindrical portion (32b, 34b) having a substantially smooth surface. An ink ribbon cassette as claimed in any preceding claim in combination with an endless ink ribbon (30) which is formed by superimposing and ultrasonically bonding end portions (52, 54) of a long length of an ink ribbon made of a fabric of a synthetic resin fibre such that one side part (52') of the bonded portion of the endless ink ribbon is molten and resinified as a solid part, and the other side part (54') thereof is brought to a semi-molten state as a semi-solid part, the running direction and the orientation of the endless ink ribbon being defined so as to avoid a passing mode where the resinified solid part of the bonded portion passes the printing head of the printer in a non-opposed direction when the ink ribbon cassette is mounted on a printer.

Inventors: AKUTSU JUNJI, KUBOTA MASAYUKI, SATO MINAKO, SUGIE MASARU, UEMURA HISASHI, AKUTSU, JUNJI, KUBOTA, MASAYUKI, SATO, MINAKO, SUGIE, MASARU, UEMURA, HISASHI
Applicants: FUJITSU ISOTEC LTD, FUJITSU ISOTEC LIMITED
Application year: 1994
Main classification: B41J32
IPC codes: B41J33, B41J32, B41J35